Q1 : A cluster has 4 nodes consisting of HA1 and HA2 out of which HA1 goes down (both controllers fails but SP is up), Will HA2 be able to serve the data of the aggregate created on HA1 if portsets has been created of consuming the lif of both the HA?
What I think is the Answer to the question is "no" but according to the link below it is possible.
Quoting the information from the link provided.
"Your data is still up and good on HA2, but by limiting the access to a portset that only uses ports from HA1, you have lost access to the data, because HA1 is still the gatekeeper to that igroup and LUN."
You also need to keep in mind the idea of epsilon and quorum with a 4 node cluster. In a 4 node cluster, if 2 nodes go down, there are not enough nodes left in the cluster to quorum and the remaining two shut down data services. in a 6 node for example, if 2 fail, the remaining 4 nodes will function OK.
So, in a 6 node cluster, an aggregte created on HA1 will still be available if HA1 goes down and 4 nodes are still available maintaining quorum and serving the data from HA2 and HA3 even though the disk connected only with HA1.